This proposal outlines a clinical trial to determine whether angiotensin converting enzyme inhibition therapy alters the rate of loss of renal function and the outcome of patients with type I diabetes mellitus who manifest evidence of diabetic nephropathy. This is one of two grant applications being submitted for this project. This application provides support for the Biostatistical Coordinating Center while the other application (Dr. Edmund J. Lewis, Principal Investigator, Rush- Presbyterian-St. Lukes Medical Center) is for the clinical study. The clinical trial to determine the effect of ACE inhibition therapy is designed to study patients with type I diabetes who have proteinuria of more than 500 mg/24 hrs. and a serum creatinine of less than 2.5 mg/dl. The goal of the study is to determine whether ACE inhibition therapy prevents the progress of type I diabetic glomerulopathy. This clinical trial will involve 20-25 collaborating clinics who will admit 400 patients during a 2 yr. recruitment. The mean follow-up will be 3 yrs. The primary end point is halving of the glomerular filtration rate. The Biostatistical Coordinating Center provides support for these collaborative trials in the study design (procedures, forms randomization), execution (data processing support, editing, updating corrections, monitoring performance of clinics, patient safety data monitoring) and final statistical analysis and publications.